Russia also test fired a silo-based YARS ICBM with an
"experimental warhead" on Sept. 12, according to TASS, while Wednesday's
launch was from a mobile unit.

"It is not clear what these new "experimental" Russian reentry
vehicles (RV) are," The National Interest reported, adding that
it's possible that it was a maneuvarable reentry vehicle designed
to allude missile defense systems.

Despite Russia signing the New START Treaty with the US in 2010,
which limited the number of nuclear warheads both countries could
build, Moscow continues to increase its stockpile, according to
Defense One.

"The aggregate data shows that Russia has continued to
increase its deployed strategic warheads since 2013 when it
reached its lowest level of 1,400 warheads. Russian strategic
launchers now carry 396 warheads more," Hans M. Kristensen, of
the Nuclear Information Project at the Federation of American
Scientists, wrote last year, according to Defense One.

Here's what the RS-24 YARS ICBM can do.

Russia began developing the three-stage solid-propellant RS-24 YARS ICBM in 2004. It was first tested in 2007, and entered service in 2010.

The YARS was first launched from mobile launcher vehicles, but as of 2014, it can be fired from silos.

It's equipped with 3 MIRV nuclear warheads, each with a payload of 2,647 pounds. A MIRV (multiple independently targetable reentry vehicle) is a ballistic missile with multiple warheads, all capable of hitting different targets.